1. Field of the Invention
The present invention relates to a paper jam detection system for a folding machine of a rotary press, which includes a cutting cylinder, a folding cylinder, a jaw cylinder, and a paper guide.
2. Description of the Related Art
Technology for detecting occurrence of paper jam at a folding cylinder or a jaw cylinder of a folding machine is disclosed in, for example, Japanese Utility Model Publication (kokoku) No. S51-13135.
The paper jam detection system for a folding machine disclosed in Japanese Utility Model Publication No. S51-13135 includes photoelectric sensors for detecting paper present on corresponding cylinders of the folding machine and pulse generators which rotate together with the corresponding cylinders and generate pulses over a rotational range in which paper is expected to be present on the cylinders. When the system fails to obtain an AND result of an output signal from the photoelectric sensor and an output signal from the corresponding pulse generator, the system judges that a paper jam has occurred.
According to the publication, in the case of a jaw cylinder, a paper jam detection system includes a photoelectric sensor provided in opposition to the outer circumferential surface of the jaw cylinder and adapted to output a signal upon detection of paper gripped by a jaw mechanism of the jaw cylinder; a signal generator provided on a shaft connected to the jaw cylinder and adapted to output a signal over a rotational range in which paper is expected to be present on the jaw cylinder; and a control unit for detecting occurrence of paper jam on the basis of a signal from the photoelectric sensor and a signal from the signal generator.
The photoelectric sensor emits light from a light emitter thereof. Emitted light reflects on paper when paper is present on the outer circumferential surface of the jaw cylinder, or reflects on the glossy outer circumferential surface of the jaw cylinder when paper is absent. Utilizing a difference in the quantity of reflected light therebetween, the photoelectric sensor outputs a signal to the control unit when paper is present.
The control unit has an AND circuit for carrying out the logical AND between a signal from the photoelectric sensor and a signal from the signal generator. When no paper is present on the jaw cylinder, no signal is output from the photoelectric sensor, and the AND condition is not satisfied. In this case, the control unit judges that a paper jam has occurred, and outputs a paper jam signal.
The above-described paper jam detection system for a folding machine involves the following problems.
1. When the outer circumferential surface of the jaw cylinder, on which light emitted from the photoelectric sensor is reflected, is smudged, the quantity of reflected light decreases, potentially causing detection error. In order to prevent this problem, a worker must clean the outer circumferential surface of the jaw cylinder so as to maintain cleanliness of the surface. This cleaning work is troublesome and time-consuming, thus imposing a burden on the worker.
2. The system for detecting occurrence of paper jam through detection of presence/absence of a sheet on the outer circumferential surface of the jaw cylinder is effective when applied to straight run, which is one folding mode of the folding machine (each of sheets cut from a web is transferred from the folding cylinder to the jaw cylinder to be gripped by the jaw mechanism of the jaw cylinder and then be folded, so that every jaw mechanism holds a sheet). However, the system is not applicable to collect run, which is another folding mode of the folding machine (two sheets which have been cut from a web having two different images alternately printed thereon and which carry different printed images are superposed on each other on the folding cylinder and then transferred to the jaw cylinder to be gripped by the jaw mechanism of the jaw cylinder and be folded, so that every other jaw mechanism grips two layered sheets).
In collect run, paper is not gripped by every jaw mechanism, but is gripped by every other jaw mechanism. Therefore, when a jaw mechanism which does not grip paper reaches the sensor position, the photoelectric sensor detects the outer circumferential surface of the jaw cylinder, not paper, and thus fails to output a detection signal. As a result, since the AND condition is not satisfied in the control unit, the control unit outputs a paper jam signal in spite of no paper jam having occurred in actuality, thereby rendering the system useless for collect run.
An object of the present invention is to solve the above-mentioned problems involved in the conventional paper jam detection system and to provide a paper jam detection system for a folding machine allowing easy and quick cleaning of a reflective surface that reflects light from a photoelectric sensor, exhibiting stable performance of paper jam detection through stable reflection, and capable of performing paper jam detection in both straight run and collect run.
A paper jam detection system of the present invention is applied to a folding machine of a rotary press in which a folding cylinder, a cutting cylinder, and a jaw cylinder are disposed such that an outer circumferential surface of the cutting cylinder and an outer circumferential surface of the jaw cylinder face an outer circumferential surface of the folding cylinder with gaps held therebetween for allowing passage of paper; axially extending knives project from the outer circumferential surface of the cutting cylinder; pairs each consisting of a cutting shoulder and a pin are circumferentially arranged at an outer circumferential surface portion of the folding cylinder such that the cutting shoulders are arranged at circumferential intervals corresponding to those of the knives of the cutting cylinder and such that the pins are located adjacent to and behind the corresponding cutting shoulders in relation to a rotational direction of the folding cylinder and can project from and retract behind the outer circumferential surface of the folding cylinder; each of axially extending tucker blades is circumferentially arranged at a substantially circumferentially central position between neighboring cutting shoulders in such a manner as to be able to project from and retract behind the outer circumferential surface of the folding cylinder; jaw mechanisms are circumferentially arranged at an outer circumferential surface portion of the jaw cylinder at circumferential intervals corresponding to those of the knives of the cutting cylinder; a paper guide is provided to define a sheet transfer space together with the outer circumferential surface of the folding cylinder and the outer circumferential surface of the jaw cylinder and guide a two-folded signature gripped by the jaw mechanism; and the knife and the cutting shoulder cooperatively cut off a sheet of predetermined length from a web, while the jaw mechanism and the tucker blade cooperatively fold the sheet.
The paper jam detection system comprises an interval signal generator for generating an interval signal which assumes alternately ON and OFF states according to cutting intervals of the cutting cylinder; a signature detection mechanism comprising reflection plates each having a light reflection surface and being provided at an outer circumferential surface portion of the jaw cylinder adjacent to and behind the corresponding jaw mechanism in relation to the rotational direction of the jaw cylinder such that the light reflection surface does not project beyond a contour of the outer circumferential surface of the jaw cylinder; and a photoelectric sensor adapted to generate a reflection plate detection signal upon detection of the reflection plate and located downstream, in relation to the rotational direction of the jaw cylinder, of an end of the paper guide on a side toward the jaw cylinder at a position suited for detecting the reflection plate with a gap held between the photoelectric sensor and the outer circumferential surface of the jaw cylinder; and a control unit for outputting a paper jam signal on the basis of the interval signal from the interval signal generator and the reflection plate detection signal from the photoelectric sensor.
Preferably, the control unit comprises a paper jam signal output section for a straight-run folding mode and a paper jam signal output section for a collect-run folding mode and selectively uses the paper jam signal output sections according to a folding mode. Further preferably, the paper jam detection system further comprises a detection circuit changeover unit for outputting to the control unit an instruction signal for instructing the control unit to select the paper jam signal output section for the straight-run folding mode or the paper jam signal output section for the collect-run folding mode.
Preferably, the paper jam signal output section for the straight-run folding mode judges occurrence of paper jam on the basis of ON and OFF levels of the interval signal and an ON level of the reflection plate, and the paper jam signal output section for the collect-run folding mode judges occurrence of paper jam on the basis of the ON level of the interval signal and the ON level of the reflection plate detection signal.
Preferably, the photoelectric sensor comprises a cover whose bottom panel faces a light emission-reception surface of the photoelectric sensor and has an opening formed therein for allowing passage of light and whose side panel has an air nozzle formed therein for allowing air from an air supply to impinge on the light emission-reception surface.
Since the paper jam detection system of the invention includes reflection plates each having a light reflection surface for reflecting light emitted from the photoelectric sensor, presence/absence of a signature can be detected efficiently and reliably, and cleaning of the light reflection surfaces is neither troublesome nor time-consuming, thereby reducing a burden imposed on a worker and enhancing work efficiency.
The paper jam detection system of the invention can detect paper jam in both folding modes of straight run and collect run.